1. Field of the Invention
The present invention relates to an integrated control platform for controlling an injection molding system, and more particularly to apparatus and method for controlling an injection molding system with a single, general purpose computer which performs both the machine-control functions and the human machine interface (HMI) functions. This control architecture thus obviates the need for the analog signal processor and the programmable logic controller used in the prior art.
2. Description of the Related Art
Injection molding systems are widely used for producing great quantities of inexpensive plastic products such as plastic PET preforms which can be blown into the widely-recognized drink containers. Such injection molding systems typically include a plurality of analog and digital devices which carry out the injection molding operations. For example, extruder drives, proportional flow control valves, electric drives, heating and cooling elements, and other electro-hydro-mechanical and electro-mechanical drives are analog devices which perform injection molding functions in a well-known way. Examples of digital devices include proximity switches, clamp pressure limit transducers, digital solenoid valves, etc. Each of these analog and digital devices must not only be controlled with appropriate analog and digital commands, but they are typically provided with feedback sensors which output analog and/or digital feedback signals so that the various devices may be properly controlled to produce high-volume, quality output from the system. For example, the feedback signals may be used in closed loop control to effect real-time changes in the injection molding devices (e.g. temperature set points, injection pressure, etc.). Also, the feedback signals may be used to display operational information (e.g. status, temperature, parts count, etc.) to the operator at the human machine interface or operator control panel.
In the prior art, it was necessary to utilize an analog signal processor (ASP) to provide for real-time control of the various analog devices in the injection molding system. Likewise, it was necessary to provide a programmable logic controller (PLC) to control the various digital devices in the injection molding system. See, for example, U.S. Pat. No. 5,062,052 (incorporated herein by reference) for an example of a known injection molding system utilizing both an ASP and a PLC to control the injection molding machine. While the '052 Patent discloses a general purpose computer, its use is restricted to interfacing between the PLC and the HMI. Both the PLC and the ASP are still required to perform the injection molding operations.
The known injection molding control architecture is limited in that reconfiguration of the injection molding devices cannot be done in real time. Each of the ASP and PLC must be modified or reprogrammed to effect the change. Thus, incorporating new technologies in an injection molding system often requires that the entire system be shut down for reconfiguration. Additionally, the operational status of each injection molding system may only be ascertained at the HMI of each system. Also, injection molding machine manufacturers typically utilize proprietary architecture in their PLC's, thus limiting the variety of new processing techniques than can be applied to such machines. Furthermore, using multiple layers of ASP and PLC processing control imposes a processing penalty and a bottleneck which reduces the speed at which machine changes can be accomplished.
Thus, what is needed is a new injection molding control architecture which provides true real-time control of the injection molding system, allows rapid reconfiguration of system devices, permits the use of readily available off-the-shelf software, and allows system status and control information to be transmitted beyond the system, e.g., to the factory office or even corporate headquarters.